Crystal AB, also known as Aurora Borealis, is a type of crystal that has a multi-colored, iridescent finish. The finish is created by applying a special coating to the surface of the crystal, which creates a rainbow-like effect when light is reflected off of it. Crystal AB is often used in jewelry and other decorative items, as the iridescent finish adds a sparkly, shimmering effect. It is commonly used in crystal chandeliers, earrings, necklaces, and other fashion accessories. Crystal AB is considered a premium type of crystal due to its unique, eye-catching finish.